AQA A LEVEL CHEMISTRY PAPER 1 EXAM 2026 (Actual Exam) Questions with verified Answers (Latest Update 2026) UPDATE!! A+!!!

AQA A LEVEL CHEMISTRY PAPER 1 EXAM 2026 (Actual Exam) Questions with verified Answers (Latest Update 2026) UPDATE!! A+!!! 1. What are atoms? - ANSWER Atoms are the particles that make up everything 2. What is an element? - ANSWER An element is a substance in which all the atoms are the same 3. Where are elements shown? - ANSWER Elements are shown in the Periodic table 4. How many elements are there? - ANSWER There are around 118 elements 5. What is a compound? - ANSWER A compound is a substance that contain two or more elements chemically combined 6. Describe the properties of compounds - ANSWER The properties of compounds are usually different to the elements that they are made from 7. What is a mixture? - ANSWER A mixture is a substance with different elements or compounds not chemically combined 8. Give an example of a mixture - ANSWER An example of a mixture is sand and water as they are not chemically combined and can be separated by physical means 9. What is a molecule? - ANSWER A molecule is a substance that has any elements chemically joined 10. What does a chemical formula tell you about a molecule? - ANSWER A chemical formula tells the elements in a molecule and the number of atoms of each element 11. How is a chemical formula presented? - ANSWER Each element symbol starts with a capital letter, if there is a second letter it is in lower case 12. Give an example of a chemical formula - ANSWER 13. What are state symbols? - ANSWER State symbols show the physical state of the substance solid (s), liquid (l), gas (g), or dissolved in water (aq) 14. Name three properties of Metals - ANSWER • Strong • Good conductors of heat and electricity • High melting and boiling points 15. Name three properties of Non-Metals - ANSWER -] • Weak • Bad conductors of heat and electricity • Low melting and boiling points 16. State the four different ways of separating mixtures - ANSWER Four different ways of separating mixtures are filtration, crystallisation, distillation or chromatography 17. Describe the process of filtration - ANSWER Pour your mixture onto the filter paper, the liquid simply passes through the filter paper into the flask. The insoluble solid cannot pass through and so it stays on the paper 18. Describe the process of crystallisation - ANSWER Use the method of filtration to filter off any excess soluble solid. Evaporate the mixture then transfer the hot mixture onto a dish. Crystals are formed when the mixture has cooled 19. Describe the process of simple distillation - ANSWER First we evaporate the mixture by heating it, the dissolved solid then vaporises. These vapours condense in the condenser, the dissolved solid then flows into the beaker and liquid stays in the flask 20. Describe the process of chromatography - ANSWER Take a strip of filter paper and draw a line on the bottom of the paper. Put a small drop of ink on the line, take a jar full of water up to the line and put the filter paper in. As the water moves up we see different colours on the paper these are the dyes in the ink 21. What were the early ideas of the structure of atoms? - ANSWER Early ideas of the structure of atoms stated that they are tiny spheres that cannot be divided 22. What is the plum pudding model? - ANSWER The plum pudding model is what scientists suggested is the structure of atoms is after the discovery of the electron 23. Describe the plum pudding model - ANSWER The plum pudding model suggested that an atom is a ball of positive charge with negative electrons in embedded in it 24. electronegativity - ANSWER the power of an atom to attract a PAIR of electrons in a covalent bond. 25. Why are hydrocarbons not polar - ANSWER electronegativities of hydrogen and carbon are similar 26. Why is something like CCl4 non polar? - ANSWER the bonds are arranged symmetrically about the centre, so the partial charges is the same on each side of the molecule hence they cancel 27. Strength of Intermolecular Forces from Least to Greatest - ANSWER van der waals < dipole- dipole < Hydrogen bonding 28. What affects the strength of van der waal forces? - ANSWER the strength depends on the number of electrons in a molecule and how close they can be together (straight vs branched) 29. Why does more electrons affect van der waal forces? - ANSWER they will have larger fluctuations in electron density. This leads to larger temporary dipoles and stronger dipole-dipole interactions. 30. another name for van der waals - ANSWER induced dipole-dipole interactions 31. When do you find hydrogen bonding? - ANSWER when you have a hydrogen atom bonded to a NOF element 32. Hydrogen bonds are strong as... - ANSWER the hydrogen atom is very small and it has a high charge density. 33. trigonal pyramidal (+ bond angle) - ANSWER • 3BP • 1LP • 107 degrees 34. Bent (+Bond angle) - ANSWER • 2 BP • 2 LP • 104.5 degrees 35. square planar (+bond angle) - ANSWER • 4BP • 2LP • 90 degrees 36. How much do LP reduce the bond angle by and why? - ANSWER by 2.5 degrees as they repel more than bonding pair electrons 37. ideal gas law - ANSWER PV=nRT 38. this states that every gas occupies the same volume under the same conditions. 39. How do you find the mole fraction? - ANSWER dividing the number of moles of A by the total number of moles of gas 40. partial pressure - ANSWER mole fraction x total pressure 41. How to find Kp - ANSWER curly brackets 42. Kp vs Kc - ANSWER The two approaches are equivalent, but it's much easier to measure the partial pressure of a gas than the concentration of the gas. 43. What happens if you increase the pressure of a closed system? - ANSWER the system will decrease the pressure by favouring the reaction that removes moles of gas. 44. what doesn't affect Kp or Kc? - ANSWER pressure, concentration, catalyst Does changing the pressure alter Kp? - ANSWER Changing pressure does not alter Kp. [Co(H2O)6]2+ - ANSWER Pink solution [Co(NH3)6]2+ - ANSWER Straw coloured solution Mn2+ - ANSWER Pale pink solution chlorine with water in sunlight - ANSWER 2HClO(aq) -> 2HCl(aq) + O2(g) overall: 2Cl2(g) + 2H2O(l) -> 4HCl(aq) + O2(g) Kw= - ANSWER Ka x Kb ph of diluting acid - ANSWER [H+ ] = [H+ ]old x (old volume /new volume) Where is the equivalence point on a titration curve? - ANSWER the mid point of the vertical portion When a weak acid has been reacted with exactly half the neutralisation volume of alkali, the above calculation can be simplified considerably. At half neutralisation we can make the assumption that [HA] = [A-] ka = [H+ ] [CH3CO2 - ] [ CH3CO2H ] So [H+ (aq)] = ka And pH = pka - ANSWER At half neutralisation what assumptions can we make? - ANSWER [HA] = [A-] So [H+ (aq)] = ka and pH = pka why does diluting a buffer solution not change pH? - ANSWER he ratio of [HA]/[A-] will stay constant as both concentrations of salt and acid would be diluted by the same proportion. percentage atom economy - ANSWER Mass of useful products / Mass of all reactants x 100 Mass Concentration - ANSWER mass of solute/volume of solution how do you go from mol dm^-3 to g dm^-3 - ANSWER conc in g dm-3 = conc in mol dm-3 x Mr Describe how Rutherford carried out the gold foil experiment - ANSWER Rutherford took a piece of gold foil, he then fired tiny positive alpha particles at the gold foil What did Rutherford observe in the experiment? - ANSWER Rutherford observed that most of the particles when straight through the gold foil and sometimes the alpha particles bounce back of the gold foil What did Rutherford discover from these observations? - ANSWER Rutherford discovered that atoms are mainly empty space as most of the alpha particles went straight through the gold atoms and that the nucleus of the atom is very small as only a small number of alpha particles bounce back Describe the structure of the nuclear model - ANSWER The nuclear model states that most of an atom is empty space, in the centre is the nucleus which contains protons and neutrons around the edge we find electrons What is the Relative mass and the relative charge of protons, neutrons and electrons? - ANSWER Why do atoms have the same number of protons as electrons? - ANSWER Because atoms have have no overall charge What is an Ion? - ANSWER An ion is a charged particle, it is possible to get positive or negative ions What is an Isotope? - ANSWER Atoms of the same element with different numbers of neutrons are called isotopes What is the mass number of an element? - ANSWER The mass number is the number on the top of an element it is the number of proton and neutrons combined What is the atomic number of an element? - ANSWER The atomic number is the number on the bottom it is number of protons in an atom, which is the same as the number of electrons How many electrons can you fit in the first, second and third shells? - ANSWER Shell 1 : 2 electrons Shell 2 : 8 electrons Shell 3 : 8 electrons What is an Electronic structure? - ANSWER A set of number to show the arrangement of electrons in their shells, eg. [2,6] C2 The periodic table - ANSWER What did John Newlands periodic table look like? - ANSWER He arranged the elements in order of increasing atomic mass, he saw that every eighth element reacted in a similar way What did Dmitri Mendeleev's periodic table look like? - ANSWER He arranged the elements in order of increasing atomic mass, he switched the order of some elements to the fitted in the patterns of other elements. He left gaps for undiscovered elements What does the modern periodic table look like? - ANSWER Elements are arranged in order of atomic number, the elements are organised in groups and periods which have the similar properties Why are elements in the periodic table grouped the way they are? - ANSWER Elements with similar chemical properties are grouped together in groups Why do elements in a group have similar chemical properties? - ANSWER Elements in a group have similar chemical properties because they all have the same number of electrons in their outer energy level therefore react similarly What are the names of group 1, 2, 7 and 0? - ANSWER Group 1: alkali metals Group 2: alkaline earth metals Group 7: halogens Group 0: noble gases Where are the metals and non-metals located on the periodic table? - ANSWER What happens to metals when they react? - ANSWER When metals react they lose electrons to achieve a full outer energy level What ions do metals from group 1 and 2 form? - ANSWER Group 1 form 1+ ions Group 2 form 2+ ions Name the elements in Group 1 - ANSWER Lithium, Sodium, Potassium, Rubidium, Cesium, Francium Describe the reaction of a group 1 metal and oxygen in terms of electrons - ANSWER In the reaction one group 1 metal transfers its outer electron to the oxygen another group 1 metal does the same, now all the atoms have a full outer energy level. The metals have a 1+ charge and the oxygen has a 2- charge Describe the reaction of a group 1 metal and chlorine in terms of electrons - ANSWER In the reaction a group 1 metal transfers its outer electron to the chlorine, now both atoms have a full outer energy level. The metals have a 1+ charge and the chlorine has a 1- charge What is the word equation for the reaction of group 1 metals and water? - ANSWER Metal + Water → Metal Hydroxide + Hydrogen Describe the reaction of the first three group 1 metals and water - ANSWER When water reacts with lithium the reaction is fast and there is fizzing. When it reacts with sodium the reaction is very fast and gas is produced. When it reacts with potassium the reaction is extremely fast and there is a small flame. In all the reactions the water turns alkaline Describe the correlation of the reactivity of a group 1 metal and it's location in the table - ANSWER Group 1 metals react faster as you move down the column Why are group 1 metals more reactive as we move down the group? - ANSWER As we move down the group the outer electron is less attracted to the nucleus and easier to lose because it has a greater distance between the positive nucleus Name some properties group 1 metals - ANSWER Group 1 metals have low melting points and a low density, they are soft metals and react very rapidly What elements are in group 7? - ANSWER Fluorine, Chlorine, Bromine, Iodine, Astatine How do group 7 elements achieve full outer shells? - ANSWER Group 7 elements need 1 electron to fill their outer shell so they just share an electron with another group 7 element, this is known as covalent bonding Describe the correlation of the melting and boiling point of a group 7 element and it's location in the table - ANSWER Group 7 elements have a higher melting and boiling point as you move down the column What is formed when group 7 elements react with non-metal atoms? - ANSWER Group 7 elements form covalent compounds when they react with other non-metal atoms so the electrons are shared What is formed when group 7 elements react with metals? - ANSWER Group 7 elements form ionic compounds when they react with metals so the electrons are transferred When a group 7 element reacts with a metal what charges does the group 7 element have? - ANSWER When a group 7 element reacts with a metal the group 7 element gains and electron and forms a 1- ion Describe the correlation of the reactivity of a group 7 element and it's location in the table - ANSWER Group 7 elements have a lower reactivity as you move down the column Why is it harder for an element at the bottom of the group to gain an electron that an element at the top of the group? - ANSWER An element at the top has less distance between the nucleus and the outer energy level so it gains electrons easier, an element at the bottom has a greater distance between the nucleus and the outer energy level so it is harder to gain electrons Explain what happens in a displacement reaction - ANSWER A more reactive halogen can displace a less reactive halogen from an aqueous solution of its salt Give an example of a displacement reaction - ANSWER Sodium Bromide + Fluorine → Sodium + Bromine Fluoride What elements are in group 0? - ANSWER Helium, Neon, Argon, Krypton, Xenon, Radon Why are group 0 elements unreactive? - ANSWER Group 0 elements have full outer shells and so they don't need to react to fill up their shells Describe the correlation of the melting and boiling point of a group 0 element and it's location in the table - ANSWER Group 0 elements have a lower melting and boiling point as you move down the column Where are transition metals located? - ANSWER Transition metals are located in the centre of the periodic table Name some properties of transition elements - ANSWER Transition metals are hard and strong and have a high density and melting point, they are good conductors of heat and electricity. They for coloured compounds and can be used as catalysts C3 Structure and bonding - ANSWER What are the three states of matter? - ANSWER The three states of matter are solids, liquids and gases What is the particle theory? - ANSWER The particle theory describes the movement and arrangement of particles Describe the particles in a solid - ANSWER The particles in a solid are packed closely together in a fixed arrangement, they vibrate constantly Describe the particles in a liquid - ANSWER The particles in a liquid are close together in a changing, random arrangement, they can move around Describe the particles in a gas - ANSWER The particles in a gas are much further apart in a random arrangement, they move very quickly When does a solid become a liquid? - ANSWER A solid turns into a liquid when it reaches it's melting point. As the temperature increases the particles vibrate faster until the forces between them breaks and a liquid is formed When does a liquid become a gas? - ANSWER A liquid turns into a gas when it reaches it's boiling point. As the temperature increases the particles move around faster, at the boiling point bubbles of gas form and rise to the surface and a gas is formed How are the forces between particles affected by melting and boiling points? - ANSWER Substances with higher and melting and boiling points have stronger forces between the particles How do elements form compounds? - ANSWER Elements form compounds by gaining or losing electrons or by sharing electrons In ionic bonding what two types of element react? - ANSWER In ionic bonding a metal reacts with a non-metal How are full outer energy levels achieved in ionic bonding? - ANSWER Electrons from the metal is transferred to the non-metals to give both elements full outer shells How do ionic compounds achieve full outer shells? - ANSWER Ionic compounds transfer electrons to achieve full outer shells What ions do Group 1, 2, 3, 5, 6 and 7 elements form? - ANSWER Group 1/ 1+ Group 2/ 2+ Group 3/ 3+ Group 5/ 3- Group 6/ 2- Group 7/ 1- Describe the structure of an ionic compound - ANSWER Ionic compounds form a giant ionic lattice where every positive ion is surrounded by a negative ions What are ionic compounds held together by? - ANSWER Ionic compounds are held together by strong electrostatic forces What are the properties of ionic compounds - ANSWER The properties of ionic compounds are that they can transfer electrons when they react, they have high melting and boiling points and can conduct electricity when they are not solids Why do ionic compounds have high melting and boiling points? - ANSWER Tonic compounds have high melting and boiling points because the strong electrostatic forces require a lot of heat energy to break Why can't ionic compounds conduct electricity when they are solids? - ANSWER Ionic compounds can't conduct electricity when they are solids because the ions cannot move, they are locked in place by strong electrostatic forces Why can ionic compounds conduct electricity when they are liquids or dissolved in water? - ANSWER Ionic compounds can conduct electricity when they are liquids or dissolved in water because the ions can now move and carry the charge In covalent bonding what two types of element react? - ANSWER In covalent bonding happens between two non-metals How are full outer energy levels achieved in covalent bonding? - ANSWER In covalent bonding full outer energy levels are achieved by two non-metals sharing electrons What are the properties of covalent molecules - ANSWER The properties covalent molecules are that they share electrons when they react, they have a low melting and boiling points and cannot conduct electricity Why do Covalent Molecules have a low melting and boiling point? - ANSWER Covalent Molecules have a low melting and boiling point because the bond between the molecules is weak and so it doesn't need a lot of energy to break the intermolecular forces Why can't Covalent Molecules conduct electricity ? - ANSWER Covalent Molecules can't conduct electricity because they don't have an overall electric charge What state are giant covalent molecules at room temperature? - ANSWER Giant covalent molecules are solids at room tempreature Do giant covalent molecules have high or low melting and boiling points? - ANSWER Giant covalent molecules have high melting and boiling points because they have millions of strong covalent bonds Name three giant covalent molecules - ANSWER Three giant covalent molecules are diamond, silicon dioxide and graphite What element is diamond formed from? - ANSWER Diamond is formed from the element carbon How many bonds does Carbon form? - ANSWER Carbon forms 4 bonds Describe the structure of a diamond - ANSWER Diamond has a giant molecular structure. Each carbon atom is covalently bonded to four other carbon atoms, diamonds contains many strong covalent bonds Can diamond conduct electricity? - ANSWER Diamond cannot conduct electricity Why can't diamond conduct electricity? - ANSWER Diamond cannot conduct electricity because there are no free electrons to carry the electrical charge Does diamond have a high or low melting and boiling point? - ANSWER Diamond has a high melting and boiling point Why does diamond have a high melting and boiling point? - ANSWER Diamond has a high melting and boiling point because it is made up of strong covalent bonds Describe the structure of silicon dioxide? - ANSWER Silicon dioxide has a giant covalent structure it is made up of silicon and oxygen atoms, each silicon atom is covalently bonded to four oxygen atoms, each oxygen atom is covalently bonded to two silicon atoms What is the melting point of Diamond? - ANSWER The melting point of diamond is 3700⁰C Does silicon dioxide have a high or low melting and boiling point? - ANSWER Silicon dioxide has a high melting and boiling point Why does silicon dioxide have a high melting and boiling point? - ANSWER Silicon dioxide has a high melting and boiling point because it is made up of strong covalent bonds and a lot of heat energy is required to break its bonds What element is Graphite made of? - ANSWER Graphite is formed from carbon In Graphite how many bonds does carbon form? - ANSWER In Graphite each carbon atom forms three covalent bonds Describe the structure of Graphite - ANSWER Graphite has a giant covalent molecular structure it contains many layers of carbon atoms each carbon atom covalently bonded to three other carbon atoms, the layers are held by weak forces between them Does graphite have a high or low melting and boiling point? - ANSWER Graphite has a high melting and boiling point Why does graphite have a high melting and boiling point? - ANSWER Graphite has a high melting and boiling point because it is made up of strong covalent bonds and a lot of heat energy is required to break its bonds Is graphite a good or bad conductor of heat and electricity? - ANSWER Graphite is a good conductor heat and electricity How do you choose a good indicator for titrations? - ANSWER If the equivalence point is within its ph range colour change What are two examples of good indicators for titrations? - ANSWER Phenolphthalein and methyl orange What ranges (and colour changes) does Phenolphthalein span over? - ANSWER Phenolphthalein changes from colourless to pink from pH 8.3 to pH 10. What ranges (and colour changes) does methyl orange span over? - ANSWER Methyl orange changes colour from red to yellow between pH 3.1 and pH 4.4. What would you use to find the equivalence point of a Weak Acid and Weak Base reaction, and why? - ANSWER use a pH meter It's hard to see the equivalence point as the change is so small (indicator not sensitive enough) what is a buffer solution? - ANSWER A solution that resists changes in pH when small amounts of an acid or a base are added Acidic buffer - ANSWER Weak acid and a salt of a weak acid (conjugate base) What assumptions do you need to make when calculating the pH of a buffer? - ANSWER That the salt is fully dissociated. That the acid is pretty much un-ionised. What does it do to assume that the salt is fully dissociated when calculating the pH of a buffer? - ANSWER We assume the salt is fully dissociated, so [A-] is just the initial salt concentration. What does it do to assume that the acid is pretty much un-ionised when calculating the pH of a buffer? - ANSWER We assume the [HA] is un-ionised, so that's just the initial acid concentration. [H+]=[A-] what does this assume? - ANSWER all the H+ has come from the acid dissociating - water dissociation is negligble What are the phases of halogens? - ANSWER Fluorine - gas. Chlorine - gas. Bromine - liquid. Iodine - solid. What's the trend going down group 7 for electronegativity? - ANSWER Electronegativity decreases as you go down Group 7 What's the trend going down group 7 for boiling points? And why? - ANSWER Boiling points increase down the group. This is because elements have more electrons as you go down Group 7. What's the trend going down group 7 for Silver halide solubility in NH3? - ANSWER Solubility in ammonia decreases as you go down Group 7. Which group 7 molecule is the most oxidising? - ANSWER Fluorine is the most oxidising element because it is the most electronegative. What halide ion is the most reducing? - ANSWER Iodide ions are the most reducing. When group 7 react with H2SO4 what products are made? - ANSWER F or Cl -> HCl or HF. Br -> SO2 and Br2 I -> H2S, S, SO2 Observations about H2S? - ANSWER It's a TOXIC molecule that smells like eggs What is the reaction used in water treatment to kill bacteria (no sunlight)? - ANSWER Cl2(g) + H2O(l) -> HCl(aq) + HClO(aq) -> 2H+(aq) + ClO−(aq) + Cl−(aq) What is the reaction of Cl2 with water in sunlight? - ANSWER 2Cl2(g) + 2H2O(l) ⇌ 4HCl(aq) + O2(g) What are the risks of treating water with chlorine? - ANSWER Cl2 (g) is toxic. Cl (l) on the skin or eyes causes burns. Water contains trace organic compounds. Chorine will chlorinate hydrocarbons and many of these chlorinated hydrocarbons are carcinogenic. Benefits of water treatment with chlorine? - ANSWER Water treatment kills harmful bacteria. The increased cancer risk is small, but a cholera epidemic would kill thousands. disproportionation reaction - ANSWER an element in one oxidation state is simultaneously oxidized and reduced How do you make bleach? - ANSWER When Cl2 is added to sodium hydroxide, you get sodium chlorate(I) and sodium chloride. What simple molecules do S and P form? - ANSWER S forms S8(s). P forms P4(s) What solution would you use to test a solution of potassium sulphate? - ANSWER Barium nitrate is commonly used while testing for sulphates Why is nitric acid added before the test of Ba(NO3)2 with potassium sulphate? - ANSWER Nitric acid is added to eliminate the possibility of carbonates BaCO3 gives white precipitate NO3 + CO3 gives CO2 (fizzing) Mass of proton, neutron, electron - ANSWER proton: 1 neutron: 1 electron: 1/2000 Why are covalent bonds strong? - ANSWER Covalent bonds are strong because the shared electrons are attracted to the nucleus of both atoms. Dative Bond (Coordinate Bond) - ANSWER the shared pair of electrons in the covalent bond come from only one of the bonding atoms What type of structure does diamond have? - ANSWER Giant covalent structure How many bonds for a carbon atom in diamond? - ANSWER 4 Why is diamond hard and why is that useful? - ANSWER lots of strong covalent bonds in diamond. is used as a cutting tool to cut other materials. Why doesn't diamond conduct electricity? - ANSWER because there are no delocalised electrons in the diamond structure. What melting point does diamond have? - ANSWER a high melting point Why is diamond an excellent thermal conductor? - ANSWER Diamond has a very rigid structure. This means that vibrations can easily carry heat throughout the structure. What are the 4 properties of diamond? - ANSWER hard, high melting point, does not conduct electricity, conducts heat How many bonds does a carbon atom have in graphite? - ANSWER 3 What type of structure is graphite? - ANSWER Giant covalent structure What are the features of graphite? - ANSWER high melting point. insoluble in solvents. soft conducts electricity Why does graphite conduct electricity? - ANSWER 1 electron from every carbon atom in graphite is delocalised. This electron can move freely, so graphite can conduct electricity. Why is graphite soft? - ANSWER The carbon atoms form layers of hexagonal rings, with each layer held together by weak intermolecular forces. The layers can slide over one another easily What is graphite useful for? - ANSWER as a lubricant and as pencil 'lead' Why does graphite have a high melting point and is insoluble in solvents? - ANSWER Due to the strong covalent bonds within the sheets, graphite Graphene - ANSWER A single layer of graphite Metallic bonding - ANSWER a sea of delocalised electrons surrounding a lattice of cations Why are metals good conductors of electricity? - ANSWER because the delocalised electrons can move and carry current. Why do group 2 metals have higher melting points than group 1 metals? - ANSWER ionic charge of group 2 is stronger, leading to a greater attraction to the delocalised electrons. What are the 4 key types of structures (and give an example) - ANSWER Giant covalent: graphite metallic: Mg Ionic: NaCl Simple Covalent: O2 Why do giant covalent crystals have high mpt/bpt? - ANSWER strong covalent bonds throughout the entire structure which have to be broken. Are giant covalent structures soluble? - ANSWER No, they are insoluble Are ionic crystals soluble? - ANSWER The ions are charged, and so are soluble in polar solvents like water Why do ionic crystals have high melting and boiling points? - ANSWER Ionic crystals have strong electrostatic attractions between every anion and cation When are ionic crystals good conductors of electricity? - ANSWER When molten or in solution Why are metals generally insoluble in water? - ANSWER Metals do not generally dissolve in water. This is because many will react with water to form metal hydroxides. Why do metals have high mpt/bpt? - ANSWER due to strong electrostatic attractions orbital - ANSWER a region of space where you are likely to find an electron. Why do lone pairs repel more than bonding pairs? - ANSWER Lone pairs are held closer to the nucleus of an atom. This means they repel each other more as they are physically closer. Linear (+ bond angle) - ANSWER 180 degrees 2 BP Trigonal planar (+ bond angle) - ANSWER 120 degrees 3 BP Tetrahedral (+ Bond angle) - ANSWER 109.5 degrees 4 BP trigonal bipyramidal - ANSWER 5 BP 120 degrees from equator 90 degrees angle from equator to apex. Octahedral (+ Bond angle) - ANSWER 6 BP 90 degrees Why is graphite a good conductor of heat and electricity? - ANSWER Graphite is a good conductor heat and electricity because when the carbon atoms bond together each carbon atom has an electron that is not in a covalent bond, these delocalised electrons can move and they can conduct heat and electricity What are delocalised electrons? - ANSWER Delocalised electrons are electrons that can move meaning they can conduct heat and electricity Describe the texture of graphite - ANSWER Graphite is soft and slippery Why is graphite soft and slippery? - ANSWER Graphite is soft and slippery because graphite is made up of hexagonal rings in on top of each other and there are no covalent bonds between the layers so the layers can slide making graphite soft and slippery Describe the structure of graphene - ANSWER Graphene is a single layer of graphite and it is one atom thick Is graphene a good or bad conductor of electricity? - ANSWER Graphene is a good conductor of electricity Why is graphene a good conductor of electricity? - ANSWER Graphene is a good conductor of electricity because it has delocalised electrons Is graphene strong or weak? - ANSWER Graphene is very strong Describe the structure of fullerenes - ANSWER Fullerenes are molecules of carbon atoms with hollow shapes they have hexagonal rings of carbon atoms, however they can also have rings with five or seven carbon atoms Name an example of a fullerene - ANSWER An example of a fullerene is Buckminsterfullerene What can fullerenes be used for? - ANSWER Fullerenes can be used for pharmaceutical delivery, lubricants and as catalysts What are carbon nanotubes? - ANSWER Carbon nanotubes are a group of fullerenes that are shaped into long cylinders, they are made of rings formed from six carbon atoms What are the properties of carbon nanotubes? - ANSWER Carbon nano tubes have high tensile strength, they are good conductors of heat and electricity What can carbon nanotubes be used for? - ANSWER Carbon nanotubes are used to reinforce materials such as tennis rackets Describe the structure of a metal - ANSWER Metals consist of a giant structure of atoms arranged in regular layers, the electrons in the outer energy level of each atom are delocalised What are the forces of attraction between the negative delocalised electrons and the positive ions? - ANSWER There are strong electrostatic forces of attraction between the negative delocalised electrons and the positive ions What are the electrostatic attractions in metals called? - ANSWER The electrostatic attractions in metals are called metallic bonds Do metals have a low or high melting and boiling point? - ANSWER Metals have a high melting and boiling point Why do metals have a high melting and boiling point? - ANSWER Metals have a high melting and boiling point because a lot of heat energy is needed to break the strong metallic bonds Describe the trend in 1st Ionisation Energy descending group 2. [5] - ANSWER - Group II elements all form metallic bonds and exist as giant metallic structures. - In general, high melting points. - Descending Group II- ions get bigger. Therefore attraction between metal ions and delocalised electrons is weaker. - This means that melting point decreases going down the group. - Magnesium is an anomaly. It has the lowest melting point. Describe the reaction of group 2 elements with liquid water. [3] - ANSWER M (s) + 2 H2O (l) -> M(OH)2 (aq) + H2 (g) - Reactivity increases going down the group, and reactions with water become more violent as you descend the group. - Observations: bubbles, mixture heats up Describe the reaction of Magnesium with steam. [2] - ANSWER Through Mg reacts very slowly with cold water, it reacts more vigorously with steam. Mg (s) + H2O (g) -> MgO (s) + H2 (g) Describe the solubilities of group 2... a) Hydroxides b) Sulfates [4] - ANSWER a) Mg(OH)2 is sparingly soluble Solubility of hydroxides increases down the group. b) BaSO4 is insoluble Solubility of sulfates decreases going down the group. State the uses of Magnesium. [3] - ANSWER - Magnesium is used in the extraction of titanium from its ores. - Titanium oxide is converted to TiCl4 which is then reduced to titanium by reaction with magnesium in the equation: TiCl4 + 2Mg -> Ti + 2MgCl2 State the uses of Magnesium Hydroxide. [1] - ANSWER Magnesium Hydroxide aka "milk of magnesia" and is used to alleviate constipation and (as an antacid) to neutralise excess acid in the gut. State the uses of Calcium Hydroxide. [1] - ANSWER Calcium hydroxide aka "slaked lime" and is used to neutralise acidic soil. State the uses of Calcium Oxide. [2] - ANSWER Calcium oxide is used to neutralise sulfur dioxide in order to prevent acid rain. Calcium carbonate may also be used. State the uses of Barium Sulfate. [2] - ANSWER - Eaten as part of a "Barium meal", which fills the digestive system, allowing x-rays of organs to be taken, and the x-rays are absorbed by the barium sulfate. - Although barium sulfate highly toxic, not harmful as so insoluble it cannot pass through cell membranes. State the uses of Barium Chloride. [3] - ANSWER - Acidified barium chloride may be used to test for sulfate ions. - If a thick white precipitate forms then sulfate ions are present. - The barium chloride must be acidified to remove any other ions which may affect the test Describe the appearance of the halogens. [4] - ANSWER - Fluorine is a very pale yellow gas. - Chlorine is a greenish gas. - Bromine is an orange-brown liquid that vaporises easily into an orange gas - Iodine is a black solid which vaporises on heating to a purple gas Describe the trend in electronegativity going down group 7. [3] - ANSWER Fluorine is the most electronegative, and electronegativity decreases going down the group. This is because... - Larger atomic radius - More shielding Describe the trend in boiling point going down group 7. [3] - ANSWER - All non-polar diatomic molecules. - Only intermolecular forces are Van der Waals. - Strength of Van der Waals dependent on Mr, therefore MP and BP increases going down the group. During a displacement reaction, which halogen forms a halide ion? [1] - ANSWER The element highest in the group. Describe the trend in oxidising ability going down group 7. [2] - ANSWER - Decreases going down the group. - Fluorine accepts electrons most easily (most electronegative) and is the strongest oxidising agent. What is observed when... a) Bromine forms b) Iodine forms [2] - ANSWER a) Mixture turns brown/orange b) black solid forms Describe the trend in reducing ability going down group 7. [2] - ANSWER - Increases going down the group. - Iodine atoms are the most willing to release their extra election. What happens when Sodium Fluoride reacts with sulfuric acid? [3] - ANSWER Not REDOX Steamy fumes of gas released NaF (s) + H2SO4 (aq) -> NaHSO4 (aq) + HF (g) What happens when Sodium Chloride reacts with sulfuric acid? [3] - ANSWER Not REDOX Steamy fumes of gas released NaCl (s) + H2SO4 (aq) -> NaHSO4 (aq) + HCl (g) What happens when Sodium Bromide reacts with sulfuric acid? [3] - ANSWER Acidic gas forms, and brown fumes of bromine gas appear Initial acid-base reaction: NaBr (s) + H2SO4 (aq) -> NaHSO4 (aq) + HBr (g) Further reaction, reducing Sulfur from +6 to +4: 2Br- -> Br2 + 2e- 2H+ + H2SO4 + 2e- -> SO2 + 2H2O 2H+ + H2SO4 + 2Br- -> SO2 + 2H2O + Br2 What happens when Sodium Iodide reacts with sulfuric acid? [7] - ANSWER Initial acid-base reaction: NaI (s) + H2SO4 (aq) -> NaHSO4 (aq) + HI (g) Further reduction can occur in one of 3 ways: 1. Sulfur reduced from +6 to +4 2I- -> I2 + 2e- 2H+ + H2SO4 + 2e- -> SO2 + 2H2O 2H+ + H2SO4 + 2I- -> SO2 + 2H2O + I2 Observations: acidic gas forms, black solid forms 2. Sulfur reduced from +6 to 0 [ 2I- -> I2 + 2e- ] x 3 6H+ + H2SO4 + 6e- -> S + 4H2O 6H+ + H2SO4 + 6I -> S + 4H2O + 3I2 Observations: yellow solid sulfur produced and block solid (iodine) forms 3. Sulfur reduced from +6 to -2 [ 2I- -> I2 + 2e- ] x 4 8H+ + H2SO4 + 8e- -> H2S + 4H2O 8H+ + H2SO4 + 8I- -> H2S + 4H2O + 4I2 Observations: gas smelling of rotten eggs forms and black solid forms What can be observed if Fluoride ions are present when... a) nitric acid then silver nitrate added b) dilute ammonia added c) concentrated ammonia added [3] - ANSWER a) no visible change/ no precipitate b) no change c) no change What can be observed if Chloride ions are present when... a) nitric acid then silver nitrate added b) dilute ammonia added c) concentrated ammonia added [3] - ANSWER a) white precipitate forms b) white precipitate dissolves c) no change What can be observed if Bromide ions are present when... a) nitric acid then silver nitrate added b) dilute ammonia added c) concentrated ammonia added [3] - ANSWER a) cream precipitate forms b) cream precipitate remains c) cream precipitate dissolves What can be observed if Iodide ions are present when... a) nitric acid then silver nitrate added b) dilute ammonia added c) concentrated ammonia added [3] - ANSWER a) yellow precipitate forms b) yellow precipitate remains c) yellow precipitate remains Why must the silver nitrate be acidified? [1] - ANSWER To remove any carbonate ions present, as they could alter the results. a) State the equation for the reaction of water with chlorine, and the use for one of the products formed. [2] b) In the presence of UV radiation, a different reaction occurs. State the equation. [1] c) Alternatively, solid sodium carbondate can be added to chlorinate swimming pools. State the equation, and why swimming pools are kept slightly acidic. [2] - ANSWER a) Cl2 (g) + H2O (l) ⇌ HClO (aq) + HCl (aq) HClO, aka chloric (I) acid is an oxidising agent and kills bacteria by oxidising them. b) Cl2 (g) + 2H2O (l) -> 4HCl (aq) + O2 (g) c) NaClO (s) + H2O (l) ⇌ Na+ + -OH + HClO (aq) In alkaline solution, equilibirum moves to the left. State the equation for the reaction of sodium hydroxide with chlorine, and the use for one of the products formed. [2] - ANSWER Cl2 (g) + 2NaOH (aq) -> NaClO (aq) + NaCl (aq) + H2O (l) Sodium chlorate, NaClO, is a component of household bleach Are metals good or bad conductors of heat and electricity? - ANSWER Metals are good conductors of heat and electricity Why are metals good conductors of heat and electricity - ANSWER Metals are good conductors of heat and electricity because the delocalised electrons can move and can carry the electric charge and thermal energy Are metals malleable? - ANSWER Metals are malleable meaning they can be bent and shaped Why can metals be bent and shaped? - ANSWER Metals can be bent and shaped because the layers of atoms are able to slide over each other What is an alloy? - ANSWER An alloy is a mixture of metals Are alloys malleable? - ANSWER Alloys are not malleable Why are alloys not malleable? - ANSWER Alloys aren't malleable because the different sizes of atoms distorts the layer making it hard for them to slide over each other What is the size of a nanometre? - ANSWER A nanometre is 1 x 10⁻⁹ metre What is the size of a coarse particle? - ANSWER A coarse particle is between 1 x 10⁻⁵ and 1 x 10⁻⁶ meters What is the size of a fine particle? - ANSWER A fine particle is between 1 x 10⁻⁷ and 2.5 x 10⁻⁶ meters Name some uses of nanoparticles - ANSWER Nanoparticles are used in medicines, creams and catalysts What is a risk of nanoparticles? - ANSWER It is possible that nanoparticles can be absorbed into they body and enter our cells, this could be harmful C4 Chemical calculations - ANSWER What is the Law of Conservation of Mass? - ANSWER The law of conservation of mass states that the total mass of the reactants in a chemical reaction is equal to the mass of the product Explain why reactions involving gas appear to break the law? - ANSWER The gas in the reaction will float away so it appears to break the law What is the Relative Atomic Mass (Ar)? - ANSWER Relative Atomic Mass is the final mass that takes in consideration all the isotopes of an element How do you calculate the Ar? - ANSWER Ar= (% x Atomic mass)+ (% x Atomic mass) / 100 What is the Relative Molecular Mass (Mr)? - ANSWER Relative Molecular Mass is the mass of a molecule that takes in consideration all the isotopes of all the elements in the molecule How do you calculate the Mr? - ANSWER Calculate the Ar of each element and then add them all up What are Moles? - ANSWER Moles are used to measure chemical amounts What does 1 mole of a substance equal? - ANSWER One mole of a substance is the Ar/Mr in grams What is Avogadro's number? - ANSWER Avogadro's numbers is 6.02 x 10²³ What is the Magic triangle for calculating Mass, Moles and the Ar/Mr? - ANSWER How do we balance equations using moles? - ANSWER To balance an equation using moles we need to calculate the number of moles of all the chemicals then put the number of moles in front of the chemical the divide all the numbers with smallest number, the equation is now balanced What is the Limiting Reactant? - ANSWER The reactant that get used up first in a reaction is called the limiting reactant What does the Limiting Reactant Determine? - ANSWER The Limiting Reactant Determines the amount of product formed in a reaction What is the Yield of a Chemical Reaction? - ANSWER The Yield of a Chemical Reaction is how much you actually made What does the Percentage Yield compare? - ANSWER The Percentage Yield compares the amount made with the maximum amount that could be made How do you calculate the Percentage Yield? - ANSWER Percentage Yield = (Mass/Max Mass) x 100 Why is it not possible to achieve 100% yield in a chemical reaction - ANSWER It is not possible to achieve 100% yield in a chemical reaction as some of the product may be lost and the reactants may react in differently way so we don't get the product expected, reversible reactions may not go to completion What is atom economy? - ANSWER Atom economy is a measure of the amount of starting materials that end up as useful products Why is reducing the amount of unwanted products useful? - ANSWER Reducing the production of unwanted products saves money and increases sustainable by not wasting resources How do you calculate atom economy? - ANSWER Atom Economy = (M/Ar of Desired product/ M/Ar of reactants) x 100 Why can't the atom economy be over 100%? - ANSWER The atom economy can't be over 100% because that would mean we're creating atoms which is impossible What does the concentration of a solution tell you? - ANSWER The concentration of a solution tells us the number of moles of a solute in a given volume of the solution What is the unit used to measure concentration? - ANSWER The unit used to measure concentration mol / dm³ What is the concentration magic triangle? - ANSWER How many centimeters is one decimetre? - ANSWER 1000 cm = 1 dm How many decimetres of volume does one mole of gas occupy? - ANSWER One mole of gas occupies a volume of 24dm³ What is tempreature is room temperature? - ANSWER Room temperature is 20⁰C How do calculate volume? - ANSWER Volume= Number of moles x 24 What are titrations used for? - ANSWER Titrations are used to find the exact volumes of acid and alkali that react with each other How do you carry out a titration? - ANSWER Fill up a flask with 25cm³ of sodium hydroxide solution, then add 5 drops of indicator to the solution, then place the flask on a white tile so we can see the colour change. Fill a burette with sulfuric acid. Slowly add the acid into the alkali until it nuetralsises, read the volume, record the results on the burette C5 Chemical changes - ANSWER What is formed when a metal reacts with oxygen? - ANSWER When a metal reacts with oxygen a metal oxide is formed What is the word equation for the reaction of metals and oxygen? - ANSWER Metal + Oxygen → Metal oxide What happens in an oxidation reaction? - ANSWER In an oxidation reaction oxygen is gained What happens in an reduction reaction? - ANSWER In an reduction reaction oxygen is lost What is the word equation for the reaction of a group 1 metal and water? - ANSWER Metal + Water → Metal Hydroxide + Hydrogen What is the word equation for the reaction of a calcium and water? - ANSWER Calcium+ Water → Calcium Hydroxide + Hydrogen What is the Reactivity Series? - ANSWER The reactivity series places metals in increasing order of reactivity What is a mnemonic to remember the reactivity series? - ANSWER POPULAR SCIENTISTS LIKE CREATING MANY ANNOYING ZIGZAGS IN TURKEY LIONS CHASE SALTY GOATS What type of ion does a metal form when it reacts? - ANSWER Metals lose electrons when they react and so they form positive ions What does the reactivity of a metal depend on? - ANSWER The reactivity of a metal depends on its ability to lose electrons and form a positive ion Where are unreactive metals such as gold found? - ANSWER Unreactive metals such as gold are found in the Earth Where are reactive metals such as iron found? - ANSWER Reactive metals such as iron are found in compounds, in the case of iron it is found in a mineral of iron oxide What is reduction? - ANSWER Reduction is gain of electrons What is oxidation? - ANSWER Oxidation is loss of electrons What is a displacement reaction? - ANSWER Displacement Reactions are reactions in which a more reactive element replaces a less reactive element in one of its compounds or in a solution What is needed for a displacement reaction? - ANSWER The element being displaced need to be less reactive than the element that is displacing it Show an example of a displacement reaction - ANSWER Magnesium + Iron Oxide → Magnesium Oxide + Iron Have the iron atoms been oxidised or reduced? - ANSWER The iron atoms have been reduced because they lost electrons Have the magnesium atoms been oxidised or reduced? - ANSWER The magnesium atoms have been oxidised because they gained oxygen How is carbon used to extract elements? - ANSWER The carbon displaces the less reactive element Give an example of how carbon would be used to extract iron from iron oxide - ANSWER Carbon + Iron Oxide → Carbon Dioxide + Iron Give an example of an acid - ANSWER An example of an acid is hydrochloric acid, HCl What do acids produce in aqueous solution? - ANSWER Acids produce hydrogen ions in aqueous solution Give an example of an acid producing hydrogen ions - ANSWER HCl → H⁺ + Cl⁻ What are bases? - ANSWER Bases are chemicals which can neutralise acids and produce a salt and water Give an example of a base - ANSWER A example of a base is copper oxide What are bases that are soluble in water called? - ANSWER Bases that are soluble in water are called alkalis What do aqueous solutions of alkalis contain? - ANSWER Aqueous solutions of alkalis contain hydroxide ions Give an example of an aqueous solution of alkalis that contains hydroxide ions - ANSWER NaOH → Na⁺ + OH⁻ What is the pH scale? - ANSWER The pH scale is a scale from 1-14 that tell us the acidity or alkalinity of a solution What do colours towards red show? - ANSWER Colours towards red show an acidic solution What do colours towards purple show? - ANSWER Colours towards purple show an alkali solution What happens when you react an acid with an alkali? - ANSWER A neutralisation reaction occurs, the hydrogen ions react with hydroxide ions to form water What element do all acids contain? - ANSWER All acids contain hydrogen What is the word equation for the reaction between an acid and a metal? - ANSWER Acid + Metal → Salt + Hydrogen What are the endings of salts produced from hydrochloric acid? - ANSWER Hydrochloric acid produces salts that end in -chloride What are the endings of salts produced from sulfuric acid? - ANSWER Sulfuric acid produces salts that end in -sulfate What are the endings of salts produced from nitric acid? - ANSWER Nitric acid produces salts that end in -nitrate What is formed when hydrochloric acid reacts with magnesium? - ANSWER Hydrochloric Acid + Magnesium → Magnesium Chloride + Hydrogen What is formed when sulfuric acid reacts with iron? - ANSWER Sulfuric Acid + Iron → Iron Sulphate + Hydrogen What happens to the elements in the reaction between an acid and metal? - ANSWER The metal displaces the hydrogen from the acids to form a salt and the hydrogen is released as a gas What is formed when an acid reacts with a base? - ANSWER Acid + Base → Salt + Water What is formed when an acid reacts with an alkali? - ANSWER Acid + Alkali → Salt + Water What type of ions do salts contain? - ANSWER Salts contain a positive ion which comes from the base or alkali and a negative ion which comes from the acid What is formed when an acid reacts with a metal carbonate? - ANSWER Acid + Metal Carbonate → Salt + Water + Crabon dioxide How do you make copper salt? - ANSWER Add copper oxide to sulphuric acid and stir, warm gently. The solution turns blue showing that copper sulphate is being formed, excess black copper oxide can be seen. Filter the solution to remove excess copper oxide and evaporate the water so that crystals of copper sulphate start to form. Stop heating when you see the first crystals appear at the edge of the solution , leave the rest of the water to evaporate, this gives you large crystals. Any small excess of solution on the crystals can be removed by dabbing between filter papers, then leaving to dry What are strong acids? - ANSWER Strong acids are acids that fully ionise in aqueous solutions How can we tell if an acid is a strong acid? - ANSWER We can tell if an acid is a strong acid by looking at it's equation, strong acid equations go only one way What are weak acids? - ANSWER Weak acids are acids that partially ionise in aqueous solutions How can we tell if an acid is a weak acid? - ANSWER We can tell if an acid is a weak acid by looking at it's equation, weak acid equations are reversible C6 Electrolysis - ANSWER What is electrolysis? - ANSWER Electrolysis is the processes that uses electricity to break down ionic compounds into elements Why can't solid ionic compounds conduct electricity? - ANSWER Solid ionic compounds cannot conduct electricity because the ions are locked in place by strong electrostatic forces and cannot move Why can melted ionic compounds conduct electricity? - ANSWER Melted ionic compounds can conduct electricity because the electrostatic forces are broken and the ions can move What are electrolytes? - ANSWER Electrolytes are liquids or solutions that can conduct electricity they are the solution being broken down What is the equipment used to preform electrolysis? - ANSWER In electrolysis there are two electrodes, the negative cathode and the positive anode and there is an electrolyte solution What are electrodes usually made of? - ANSWER Electrodes are made of inert substance that doesn't react with the products such as graphite Describe the stages of the electrolysis of aluminium oxide - ANSWER The aluminium oxide is mixed with cryolite to lower the melting point, the solution is used as the electrolyte, the positive aluminium ions are attracted to the cathode and the negative oxide ions are attracted to the positive anode, the aluminium is reduced and the oxide is oxidised Describe the stages of the electrolysis of copper sulfate - ANSWER Copper sulfate solution is used as the electrolyte, the positive copper ions are attracted to the cathode and the negative sulfate ions are attracted to the positive anode, the copper is reduced and the sulfate is oxidised Why must the anode be replaced regularly? - ANSWER The anode must be replaced regularly because the oxygen produced at the anode reacts with the carbon in the graphite forming carbon dioxide gas C7 Energy changes - ANSWER What are exothermic reactions? - ANSWER Exothermic reactions are reactions that transfer energy to their surroundings What happens to the temperature of the surroundings in an exothermic reaction? - ANSWER In an exothermic reaction the temperature of the surroundings gets increases Give three examples of exothermic reactions - ANSWER Three examples of exothermic reactions are combustion, oxidation and neutralisation What are two uses of exothermic reactions? - ANSWER Two uses of exothermic reactions are hand warmers and self-heating cans What is the energy profile diagram for a exothermic reaction - ANSWER In an exothermic reaction what has more energy the reactants or the products? - ANSWER In an exothermic reaction the reactants have more energy that the products Why do the reactants have more energy that the products in an exothermic reaction? - ANSWER In an exothermic reaction the reactants have more energy that the products because energy is being transferred from the reaction to the surroundings What does the difference between the energy of the reactants and the energy the products tell us? - ANSWER The difference between the energy of the reactants and the energy the products tells us the energy that has been released to the surroundings What are endothermic reactions? - ANSWER Endothermic reactions are reactions that take in energy from their surrondings What happens to the temperature of the surroundings in an endothermic reaction? - ANSWER In an endothermic reaction the temperature of the surroundings decreases Give an example of endothermic reactions - ANSWER An example of a endothermic reaction is thermal decompostion What are two uses of endothermic reactions? - ANSWER Endothermic reaction are used in cold packs and cooking What is the energy profile diagram for a endothermic reaction - ANSWER In an endothermic reaction what has more energy the reactants or the products? - ANSWER In an endothermic reaction the products have more energy that the reactants Why do the products have more energy that the reactants in an endothermic reaction? - ANSWER In an endothermic reaction the products have more energy that the reactants because energy has been taken in from the surroundings What does the difference between the energy of the reactants and the energy the products tell us? - ANSWER The difference between the energy of the reactants and the energy the products tell us the amount of energy taken in by the reaction What is needed for reaction to occur? - ANSWER Reactions can only occur when particles collide with each other with sufficient energy What is the activation energy? - ANSWER Activation energy is the minimum amount of energy that particles need in order to react Where is the activation energy located on a energy profile diagram? - ANSWER In an exothermic reaction energy changes are shown as positive or negative? - ANSWER In an exothermic reaction energy changes are shown as negative Why are energy changes shown as negative in exothermic reactions? - ANSWER In an exothermic reaction energy changes are shown as negative because energy has been transferred In an endothermic reaction are energy changes shown as positive or negative? - ANSWER In an exothermic reaction energy changes are shown as postive Why are energy changes shown as positive in endothermic reactions? - ANSWER In an endothermic reaction energy changes are shown as positive because energy has been gained Is making bonds exothermic or endothermic? - ANSWER Making bonds releases energy so it is exothermic Is breaking bonds exothermic or endothermic? - ANSWER Breaking bonds requires energy so it is endothermic What is the energy value? - ANSWER The energy value tells us the energy required to break that bond How do you calculate the energy change of a reaction? - ANSWER To calculate the energy of a reaction you need two things the structure of the molecules and the energy value of each bond, add up the energy need to break all the reactants and the energy need to make all the products, the difference between the energy needed for the reactants and the energy needed for the products is the energy change What is an electrolyte? - ANSWER An electrolyte is a solution that can conduct electricty Give an example of an electrolyte - ANSWER An example of an electrolyte is an ionic compound What is one way of producing electricity? - ANSWER One way of producing electricity is to take two different metals and place them into an electrolyte What is the half equation for a negative electrode? - ANSWER 2H₂ → 4H⁺ + 4e⁻ What is the half equation for a positive electrode? - ANSWER O₂ + 4H⁺ + 4e⁻ → 2H₂O What is the overall equation? - ANSWER 2H₂ + O₂ → 2H₂O Describe the nuclear model of an atom. [2] - ANSWER - Nucleus containing of protons and neutrons. - Surrounded by electrons in energy levels. State the relative mass and charges of a proton [2]. - ANSWER Mass: 1 Charge: +1 State the relative mass and charges of a neutron. [2] - ANSWER Mass: 1 Charge: 0 Define atomic number (Z). [1] - ANSWER The number of protons in an atom. State the relative mass and charges of an electron. [2] - ANSWER Mass: 1/1840 Charge: -1 Define mass number (A). [1] - ANSWER The number of protons and neutrons combined in an atom Define isotope. [1] - ANSWER Atoms with the same number of protons but a different number of neutrons. Describe the chemical properties of two isotopes of the same element. [2] - ANSWER -Same chemical properties. -As same electron configuration. State the uses of mass spectrometry: [4] - ANSWER - Identify elements - Determine relative molecular mass. - Determine isotopic mass. - Determine relative abundance of isotopes. Why is mass spectrometry done in a vacuum? [1] - ANSWER Prevent positive ions from colliding with molecules in the air. Describe electrospray ionisation: [4] - ANSWER - Sample dissolved in volatile solvent. - Injected through a fine hypodermic needle giving a fine mist/aerosol. - Tip of needle connected to positive terminal of a high voltage. - Each molecule gains a proton as it leaves the needle. Describe acceleration: [2] - ANSWER - The positive ions are attracted to a negatively charged plate and accelerate towards it. - All ions accelerate forward so that they have the same kinetic energy, but reach different velocities due to their varying masses. (lighter → faster) Describe ion drift: [2] - ANSWER - Some of the ions pass through a hole in the negatively charged plate, forming a beam of particles. They travel along the 'flight tube' towards the detector. - As the ions are travelling at different speeds, they drift apart further. Describe detection: [2] - ANSWER - When the positive ions hit the negatively charged detection plate, they gain an electron. - This generates a current, the size of which is proportional to the number of each type of ion. Describe data analysis: [1] - ANSWER The signal from the detector is passed to a computer which generates a mass spectrum from the current. What does each peak on the graph represent? [2] - ANSWER - Each peak represents different isotope. - Height gives relative abundance of each isotope. Give the formula for relative atomic mass: [1] - ANSWER (sum of abundances not 100) Describe where electrons are found. [3] - ANSWER - Found in shells, orbiting nucleus. - Within each shell there are sub-shells. - Within each sub-shell we find orbitals. Define orbital. [1] - ANSWER An orbital is a region within an atom that can hold up to two electrons with opposite spins. How many orbitals are there in... a) an s sub-shell b) a p sub-shell c) a d sub-shell [3] - ANSWER a) one s orbital b) three p orbitals c) five d orbitals Define highest energy electron. [1] - ANSWER The outer most electron on an atom or ion. What is stated by the Aufbau principle? [1] - ANSWER Orbitals of lower energy are always filled first. What are the exceptions to the Aufbau principle? [3] - ANSWER Cr - 3d5 4s2 Cu - 3d10 4s1 Define ionisation energy. [2] - ANSWER The amount of energy needed to remove a mole of electrons from a mole of atoms, in the gaseous state. Units kJmol-1 Why does ionisation energy increase each time? [1] - ANSWER The second electron is removed from an ion that already has a positive charge. Give the equation for 3rd ionisation energy. [1] - ANSWER Give an example of an ionic crystal, and describe its structure. [3] - ANSWER - Sodium Chloride - Each Na+ ion surrounded by 6 Cl- ions and vice versa. (6:6 configuration) - Lattice described as a cubic arrangement. Describe the structure of metallic crystals and their properties. [4] - ANSWER - Held together by metallic bonding. - Atoms are packed close together in layers, with the outer shell electrons not bound to a single atom- and instead able to move about between the layers (electrons are delocalised) - Lattice structure - Insoluble in water, though some metals will react. Describe the structure of molecular crystals and their properties. [5] - ANSWER - Molecular covalent substances exist as single molecules, held together by intermolecular forces. - Tend to exist as liquids or gases- but can also be low melting point soilds- at room temp and pressure. - Many solid molecular covalent substances form crystalline structures → molecular covalent crystals. - Molecular covalent crystals have low melting points, are brittle, and do not conduct electricity. - Mostly insoluble in water- though some polar substances dissolve and some non-polar substances react. Give two examples of molecular crystals and describe their properties [6] - ANSWER 1. Iodine Large iodine molecules pack together into a regular arrangement. Low melting point - 114°C 2. Ice Water molecules arranged regularly, forming crystalline structure. Melting point- 0°C Describe the structure of macromolecular crystals and their properties. [3] - ANSWER - Covalent b